Tablets used as medicines often have their surfaces engraved with an inscription during tablet molding or printed with letters or codes after molding in order to help product recognition. Contact printing methods have conventionally been used in the printing of tablets. For example, a method using a printing plate such as gravure printing is employed in which ink is once transferred to a soft pad and then re-transferred to tablets.
In recent years, orally disintegrating tablets that can be taken without water have gradually become common. Since the orally disintegrating tablets are vulnerable to pressure, the contact printing methods as described above may damage tablets due to the pressure of printing plates. That is, the printing methods that bring printing plates into contact with tablets may yield defective tablets. Meanwhile, scored tablets that can be split into halves along a parting line are also becoming widely available. In the printing of scored tablets, it is necessary to perform printing in accordance with the orientations of parting lines on a plurality of scored tablets that are being conveyed. In view of this, there has been increasing demand for inkjet tablet printing apparatuses that are capable of non-contact printing and capable of easily controlling print orientation.
One example of the inkjet tablet printing apparatuses is described in, for example, Patent Literature 1.